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Need milk?

The milkman cometh

Who remembers Milky the Clown, mascot for the Detroit-based Twin Pines Dairy?

In the U.S., health experts recommend adults and children 9 years of age or older consume an average of three 8 oz. servings (237 mL) of milk daily (or equivalent cheese, yogurt, or other dairy product). This amount is substantially higher than the current average adult intake of only 1.6 calcium servings daily.

Scientists supposedly have justified this relatively high recommendation to meet to reduce bone fractures and all-cause mortality risk. But recently scientists have challenged this assertion about milk’s health benefits and warned about possible adverse health outcomes.

Dairy product composition

The table below presents the nutrient composition of human milk, cow’s milk, and cheese. To increase milk production, cows have been bred to produce higher insulin-like growth factor I (IGF-I) levels. This increases the level of progestins and estrogens in their milk.

Human and Cow’s Milk and Cheese Nutrient Composition

Component

Human milk, 8oz

Whole-fat cow’s milk, 8oz

Fat-free cow’s milk, 8oz

Cheddar cheese, 37g (equals 8oz whole-fat cow’s milk)

Calories

172

149

83

149

Protein, g

2.5

7.7

8.2

8

Total fat, g

10

7.9

0.2

12.3

Saturated fat, g

4.9

4.6

0.1

7

Carbohydrate, g

16.9

11.7

12.1

1.1

Calcium, mg

78

276

298

262

Potassium, mg

125

322

381

28

Phosphorus, mg

34.4

205

246

16.79

Source: U.S. Department of Agriculture.

Milk processing has many potential positive and negative health implications. For example, pasteurization reduces brucellosis, an infectious disease characterized by high- and low-fever swings, the sweats, muscle and joint pains, weakness, tuberculosis, and other pathogen transmissions. In contrast, fermentation, used to produce aged cheese, yogurt, kefir, and other products, denatures important peptide-hormones. The process alters protein antigens (a toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies), reduces lactose content, and affects bacterial composition.

Milk and bone health

Elsie the Cow first appeared in 1936 as a mascot for the Borden Dairy Company to symbolize the “perfect dairy product.”

Experts often cite calcium’s supposed bone-health benefits as a way to rationalize this recommended high level of lifelong milk consumption. Such an assumption derives from early studies assessing calcium balance in just 155 adults in whom the estimated daily calcium intake necessary to maintain calcium balance averaged only 741 mg. These small studies had other serious limitations, including short duration (2-3 weeks) and varying habitual calcium intakes. In other studies, the threshold for estimated calcium balance occurred at approximately 200 mg per day among males who had low habitual calcium intakes.

In randomized trials that used bone mineral density as a fracture risk indicator, daily calcium supplements of 1,000-2,000 mg produced a 1-3-percent greater bone mineral density (BMD) than a placebo. If sustained, this small divergence would be important. However, after one year, the rate of BMD change among late perimenopausal and postmenopausal women equaled the placebo value, and upon discontinuing the supplementation, the small difference in BMD disappeared. Because of this transient “beneficial effect” of calcium supplementation, trials lasting one year or less can be misleading, and the 2-3-week balance studies to establish calcium requirements have limited relevance to fracture risk. In fact, higher calcium intakes may relate to higher hip fracture rates.

The figure below shows milk consumption as a proportion of total energy intake versus age-standardized hip fracture rates annually per 100,000 persons. As can be observed, countries with the highest milk and calcium intakes tend to have the highest hip fracture rates. This positive association may not be causal, however, because confounding factors like vitamin D status and ethnicity could have impacted the findings.

Milk consumption and mortality

Specialty products, like the dairy alternative oat “milk,” retail for a higher price than cow’s milk.

When comparing major protein sources from animals or plants, dairy consumption associates with lower mortality than with processed red meat and egg consumption. Similar mortality occurs for unprocessed red meat, poultry, and fish consumption, yet significantly higher than the consumption of plant-based protein sources. This figure shows the percent difference in all-cause mortality associated with protein sources. The dashed line at 0 is the reference mortality value associated with major protein dairy sources.

Comparisons reflect 3 percent of protein-energy from each source, with milk corresponding to about 500 g (two 8-oz. glasses). Data were recalculated with dairy foods as the comparison based on a 32-year follow-up in 131,342 males and females.

The conclusion from these data indicates that increases in animal-based protein sources in the diet, compared to dietary plant-based protein sources, increases all-cause mortality risk.

The conclusion from these data indicates that increases in animal-based protein sources in the diet, compared to dietary plant-based protein sources, increases all-cause mortality risk.

Conclusions

The overall evidence for adults does not support high dairy consumption to reduce fractures. Current recommendations to increase dairy food consumption to three or more milk servings per day appears unjustified. Optimal intake of milk for any individual, of course, depends on overall diet quality. If diet quality is low, especially for children in low-income environments, dairy foods can improve nutrition. In contrast, where diet quality is high, as often observed in the U.S., increased dairy intake is unlikely to provide substantial benefits. Harm is actually possible.

When consumption of milk is low, the two nutrients of primary concern, calcium and vitamin D, can be obtained from other foods (or supplements) without the potential negative consequences of excessive dairy intake. Rich sources of calcium include kale, broccoli, tofu, nuts, beans, and fortified orange juice; for vitamin D, supplements can provide adequate intake at a far lower cost than fortified milk.

References

Agnieszka Bzikowska-Jura, Aneta, et al. “The concentration of omega-3 fatty acids in human milk is related to their habitual but not current intake.” Nutrients 2019; 11:1585.

Comments

John Sapia - MPH - 68

Recommend that any future articles on milk explain that 8 oz.milk is equal to ? oz of cheese, yogurt etc. Therefore, If one consumes ? oz of cheese and/or yogurt etc. daily, with or without milk, they may be consuming equal to or more than the average adult serving of 1.6 vs 3 servings.

Vic Katch

Ethel Larsen - 1972

Interesting that among the nordic countries, Finland (my ancestral homeland) has significantly lower fracture incidence despite greater milk product consumption, but is relatively similar to its neighbor to the east, Russia.

doris shapardanis - 1972, Masters: l1977

Will White - PhD Nuclear Engineering, 2006

I note that the first graph (hip fracture rates) purports to show a trend (a helpful line is even included), but the data looks more like a random scatter. The lack of error bars (in either direction) may be an indication that the reference is unwilling to disclose the absence of any actual correlation. Disappointing, but not unexpected in a general interest article like this. I would caution the author that the subject is interesting enough without finding it necessary to exaggerate. Caveat lector.

About the Author

VICTOR KATCH has been active in the exercise, nutrition, and weight control arena for more than 40 years at the University of Michigan. He earned his undergraduate degrees in international relations (political science) and physical education (kinesiology) from California State University at Northridge. He also did undergraduate work in international relations at the prestigious University of Uppsala in Sweden. Katch's graduate degrees are from the University of California, Berkeley. He is professor emeritus in movement science in the School of Kinesiology. He has three children and five grandchildren, and is an avid exerciser who enjoys year-round walking and jogging with his wife, Heather, and playing golf whenever possible, weather permitting.